Why are the visiting hours for the ICUs (MICU, SICU), Recovery Room and High Dependency Unit (HDU) limited to 30 minutes periods?

The patients in the ICUs, Recovery Room and HDU are very ill. We need to ensure that these patients get the rest they need, and other patients are not disturbed. Research shows that limiting the visitation hours in these areas will allow patients to get more rest and to recover more quickly.